The present invention relates to control of variable speed fans utilized in computer type systems.
Fans are standard components in many commercial computers, workstations, notebook and desktop personal computer systems, and in many other electronic and mechanical systems. Fans remove heat generated due to operation of integrated circuits and other components in such systems.
The use of fans often presents certain disadvantages in various systems. For example, fan is a source of objectionable acoustic vibrations, the noise generated by the fan being a monotone non-decreasing function of the rotational rate of the motor. Also, fan often has a service life that is less than the service life of the equipment it protects, and generally a fan service life expectancy is the shorter the higher is operation rotation rate of the fan.
Additionally, fans require large operating currents, the current requirements increasing with the fan rotational rate. Such usage of large currents creates problems for low power, xe2x80x9cgreenxe2x80x9d personal computer systems.
The present invention employs simple and novel methods and apparatus for overcoming these disadvantages.
In accordance with the principles of this invention, the noise generated by at least one fan with a direct current motor, which is disposed within and ventilates a zone of a personal computer, is found to be a function of the rotational rate of the motor. In order to reduce the noise, it is necessary to reduce this rotational rate. To this end, a thermo-sensor is positioned within the zone adjacent the fan to measure the actual temperature thereof.
A controller is connected between the fan motor and a direct voltage power supply of the computer. The controller receives a first input from the sensor thereby reading the temperature in the zone and also receives an input voltage from the supply. The computer has a data file which contains for said fan a table which lists for each temperature an optimal rotational rate and also specifies a maximum allowable temperature value and recommended corresponding rotational rate value for said motor. When the actual temperature in the zone is changed during operation, the controller modifies the voltage fed to the motor in such manner as to provide the assigned optimal rotation rate.
In order to optimize the fan cooling efficiency at a given temperature, a tachometer can be integrated with the fan to measure the actual rotational rate thereof. The tachometer provides a second input to the controller thereby providing optimal reaction of the controller to variations in zone temperature.
The data file can also list first, second and third chosen modes of operation identifying respectively, suspension of normal computer operation, emergency deactuation of the computer, and generation of warning message to be received by the user. Each mode is initiated by a corresponding one of first, second and third specific listed commands when the current temperature exceeds the specified maximum. In the event that the actual temperature is not reduced below the maximum value, the controller actuates a selected one of first second and hird modes of operation in response-to a corresponding one of the first, second and third listed commands.